BOSTON, June 15 Asthma is the single most important factor to increase the risk of death from anaphylaxis, or allergic shock, says a U.S. report.Anaphylaxis is an allergic reaction affecting the entire body and it ranges from relatively mild to life-threatening.In the United States, anaphylaxis is responsible for somewhere between 500 and 1,000 deaths each year, mainly of children and adolescents. Peanuts and tree nuts such as walnuts appear to be the prime culprits, and account for most of the deaths from anaphylaxis in children, according to the new report from Harvard Medical School, "What To Do About Allergies." A person experiencing anaphylaxis may first feel flushed, sneeze, itch, and develop hives, have nasal congestion and watery red eyes. Symptoms then progress to difficulty breathing and swelling of the throat and tongue, which is sometimes associated with nausea, vomiting, and diarrhea. Blood pressure may drop, followed by fainting or loss of consciousness, shock and -- without swift treatment -- death.Those at risk for anaphylaxis should carry epinephrine -- adrenaline -- with them at all times."What To Do About Allergies" is available for $16 from Harvard Health Publications, online at the Web site health.harvard.edu. Copyright 2007 by UPI